Instant political biographies have a disconcerting way of disappearing pretty instantly. One moment you're sitting down with Bruce Anderson on John Major or John Rentoul on Tony Blair and the time is right; the next moment a tide of events and concomitant irrelevance engulfs everything. But Pollard on Blunkett breaks all known records for disposability.

Pollard, a keen and careful journalist cum academic, set out to chronicle the amazing rise of a Home Secretary and political heavyweight like no other in British history: from blindness at birth, struggling through an impoverished childhood, then onwards and upwards to leader of Sheffield council, Labour front-bencher, Cabinet minister and big Westminster beast.

Where next? he asks at the end. Could it be the Treasury once Gordon goes? Or Environment, in the wake of Beckett, as the true heir of Prescott? Is there a chance that Downing Street may beckon? Fat chance! A rush of a postscript catches up with Kimberly Quinn's contortions when nothing was yet resolved and the various 'friends' were still pushing their early toxins. Pollard puffs along behind events pondering how 'seriously Blunkett's political standing has been damaged, perhaps irreparably'. Well, we know the answer to that now. We know that a career, nipped in the Budd, will never recover its former glory. We know that wonderful rise has turned to hideous fall.

Could the Home Secretary have hung on without the pages where he slags off Patricia Hewitt, Tessa Jowell, Charles Clarke, Two Jags and a Chancellor 'floating above' the fray? Quite possibly. The inconclusive Budd report, of course, was written after he'd resigned. It wouldn't necessarily have damned if he'd been upright at the time. Downing Street in particular and the Cabinet in general didn't want to lose him through the early encounters. But those rabbitings into Pollard's tape recorder from many months before were lethal in context, seeming to spit in the face of his defenders.

They don't, to be honest, seem as inflammatory now, most passion spent. As an anodyne pre-Christmas diary penned by some sleepy political editor, the remarks would zizz by in the night. Why did they wreck him then?

'I sometimes think that I've been trying to over-prove myself,' Blunkett says at one point. And there, maybe, is a theme that binds. Had this awe-inspiring force of nature and ambition become so wrapped up with himself and his own battles, that'd he lost any sense of balance?

You could make a case for pursuing access agreements to a child you believed you had fathered, but not to carrying on in office as though nothing had happened. You could understand how a tired, angry man could rant about comradedly frailties. But put the strands together and something much more worrying emerges: a life temporarily knocked off track, a rage blazing out of control. And where does that fit with ID cards, new security agencies, Belmarsh and the baggage of re-election?

It doesn't. It re-casts the soap drama of the past few weeks as Blunkett Agonistes, a hero undone not by wily seductresses but by the tensions boiling within himself. All the things that most endear him to Pollard - his humour, his warmth, his bravery, his incorrigible self-belief, his bluff humanity - combine at the close to bring explosion, then implosion.

Can he come back? The answer doesn't rest with Tony Blair, but with David Blunkett himself. The answer depends on his finding a balance again. If and when Blunkett returns, then an updated Pollard may find shelf life again. But beware camp followers bearing tape recorders. For the moment it is only a sad testimony to hopes dashed and admiration suspended in a welter of emotion inviting sorrow, pity and awe - but no more instant biographies.